(1) Field of the Invention
This invention relates to fluid pumps and more particularly to a precision pump for adding a small adjustable precision amount of fluid to a process.
(2) Description of the Related Art
Pulsator pumps are well known to the art. In this type pump a product chamber which has an inlet and outlet valve and a diaphragm so that the volume of the product chamber is changeable. With the changing of the product chamber volume the product fluid will be pumped as is well known.
One common way of moving the diaphragm of the product chamber to change its volume is to use a fluid on the other side of the diaphragm. Pumps which utilize this method are well known; for example see SCHERGER, U.S. Pat. No. 2,578,746 or QUARVE, U.S. Pat. No. 4,068,982.
These pumps contain a pulsator fluid within the pulsator chamber which acts against the product diaphragm causing the pumping action A relief valve is used to release the positive pressure in the pulsator chamber after the diaphragm completes its stroke or "bottoms out". I.e., the design of the pump is such that the diaphragm moves between two set limits: one of which results in a maximum volume in the product chamber and the other results in a minimum volume in the product chamber. Therefore for each stroke of the pump an exactly identical amount of volume of product is displaced in the pump for every stroke. That precise volume is the maximum volume which the diaphragm is capable of displacing.
It will be noticed from SCHERGER and QUARVE, that different methods such as pressure sensitive valves and the like are known to be used to replenish the amount of liquid in the pulsator chamber and to also bleed any gas from the pulsator chamber that might become present.
Pulsator pumps are particularly adept for pumping toxic or highly volatile products. This is because there are no sealed moving parts holding the toxic liquid being pumped. I.e., there are no rotating elements or reciprocating elements extending from outside of the product chamber to inside the product chamber nor are there pistons requiring seals as in the case of a centrifugal pump or a reciprocating piston within a bore.
Before this patent application was filed applicants were aware of the following art of record in addition to SCHERGER or QUARVE, however, they do not consider any of the other patents more pertinent to their invention.
______________________________________ 3,256,824 Sebardt 3,339,464 Rietdijk 3,680,981 Wagner 3,680,985 Ginsberg 3,704,858 Dros 4,378,201 Quarve 4,416,599 DeLongchamp 4,560,324 Durieux 4,564,340 Stahlkopf ______________________________________